A surface low pressure system (90L) just east of Puerto Rico is moving to the west at 5-10 mph. This low is entangled with an upper-level low pressure system that is bringing about 30 knots of wind shear, so no development is likely today. Long range radar out of Puerto Rico shows bands of heavy rain hitting the islands and surrounding waters, but these bands are not well-organized. Satellite loops show most of the heavy thunderstorm activity is to the northeast of the low's center of circulation, and high wind shear is keeping this thunderstorm activity disorganized. This morning's QuikSCAT pass missed 90L.

The surface low is expected to separate from the upper level low tonight and move west-southwest or southwest across Puerto Rico, bringing the threat of heavy rain and flooding to the island. Recent rains have left large areas of interior and western Puerto Rico at or near saturation, and mudslides were reported yesterday in Utuado. Flooding problems and mudslides are likely across Puerto Rico and the Virgin Islands Friday and Saturday, and this is shaping up to be the most significant rain event of the fall wet season thus far for Puerto Rico.

On Friday and Saturday, 90L will move westward along or just south of Hispaniola, bringing heavy rain, flash flooding, and possible mudslides to that island. The ECMWF and NOGAPS models predict that wind shear will drop to 10-20 knots by Friday night, which may allow some slow development of the disturbance if the center remains over water. The GFS model keeps wind shear 20-30 knots through the period, and does not develop 90L. By Saturday, the storm will near Jamaica, and the ECMWF and NOGAPS models predict a tropical depression will form by Sunday. Steering currents grow weak on Monday, and the storm could stall out for many days in the Western Caribbean, in an area of low wind shear and high heat content waters. This may allow the system to intensify into a hurricane. The eventual fate of this system is highly uncertain, since steering currents will be so weak. Those of you planning to travel to the Western Caribbean next week should keep a close watch on this system. NHC has not scheduled any flights into 90L yet.

It is possible that wind shear and passage over the islands will sufficiently disrupt this disturbance so that it does not develop. However, surface pressures have fallen 2-3 mb over most of the Western Caribbean the past two days, and there is a good chance that a new area of disturbed weather will develop. One such disturbance formed yesterday south of Haiti, but has since dissipated. Unsettled rainy weather can be expected to affect much of the Western Caribbean over the coming week.

California's firesSurface maps show that the high pressure system that brought this week's strong Santa Ana winds to Southern California has now moved east and is over Colorado. The Santa Ana winds have ceased over California, and only light winds with afternoon sea breezes are expected today and for the next seven days. No precipitation is expected for at least the next week. The combination of light winds and lack of rain will make for a serious air pollution hazard in the region, until the fires are extinguished. There is still plenty of smoke over the ocean waters (Figure 2) that will get blown back over land by afternoon sea breezes over the next week.

Figure 2. Visible satellite image at 1:45 pm PDT Wednesday October 24, showing a huge area of smoke over the Pacific Ocean. Some of this smoke is being blown northward (top of image), and is expected to move over northern California and northern Nevada over next two days. This northward-moving smoke is being lifted by the flow around an approaching low pressure system, and is not expected to affect air quality near the surface. However, the smoke just offshore San Diego and Los Angeles will remain near the surface, and some of it will be pushed back over land by afternoon sea breezes. Image credit: NASA.

Now that thats oover with, I will have to admit that there is a nice flareup of convection, but due to a hostile environment (much like this chat tonight) I do not think it will develop. I will go now. Hopefully none of this will be mentioned tomorrow I liked it for the past 3 months when it was nice weather talk.

actually i think the Cimss might be right on the money. Zoom in on the 850mb the strongest region of vorticity maximum in the deep red is just ENE to NE of Puerto Rico. Matches with the night time visible imagery.

So now that you know about me, please call me immature and tell me to leave again. Whoever starts to bicker with someone else on this site is the immature one. Administration, if you are reading, please note that I am not the bickerer but the bickeree just trying to defend himself from a guy who apparently cant pick on someone his own size. Please dont ban me!!

Im looking at the news right know and they are advertising know that it can be a dangerous event. I think most people should know right know. but this event have already been a deadly one because two men died this afternoon after a car accident caused by a mudslide.

WOW! Invest 90L starting to look more impressive with each passing image. Convection starting to consolidate around the center and has begun to move WSW. TD 16 tomorrow in my opinion.

Referring to the questions of the monster ULL, the ULL is helping ventilate the system as the wind shear is not associated with the ULL. But, I agree it needs to move away from it since it will likely start to come closer.

I assume the " pr" in your handle means Puerto Rico. If so you have several hours before the worst of the weather ( which is on the E side of 90L ) impacts you. However, the rain will come before the wind as is usually the case with a sheared system

Yes...100% concern. Of all the flooding events that occur in my island almost all occurred in October and November which are the two wettest months and the culprits are tropical waves and tropical disturbances like 90L. Flooding will most likely occur as 90L moves west, we had a very heavy downpour just ended minutes ago.